Update: During the 20/20 story Remini revealed that she was asked to invite non-Scientologists Jennifer Lopez and Marc Anthony to the wedding of Tom Cruise and Katie Holmes in 2006 and that while there, church officials tried to separate her from the pop-star couple in order to convert them to the religion.

After the wedding, Remini learned that other Scientologists at the wedding had filed reports on her with the church, alleging that she displayed "horrible behavior" and "basically destroyed the wedding." One of these people, according to Remini, was Katie Holmes.

For their part, the church has told ABC that "Every claim Miss Remini has made is not only untrue but ridiculous and stupid."

Update: Katie Holmes' publicist denies that Holmes is appearing on tonight's 20/20 special about Leah Remini in statement made via email toPeople.

"Katie is not making an appearance on the special, nor is she discussing Scientology, or her former marriage, and this quote was provided through her publicist... For any outlet to suggest otherwise is misleading; I would think Leah and the book stand on their own, and don't need to trade off Katie Holmes for people to tune in."

Additionally, Holmes said through her publicist, "I regret having upset Leah in the past, and wish her only the best in the future."

This story was originally published on October 30 at 4:00 p.m.

Katie Holmes has thus far remained tight-lipped about her experience with Scientology. Tonight, the ex-wife of high-profile Scientologist Tom Cruise will speak publicly on the subject for what is reportedly the first time. The actress will appear on a 20/20 special focused on Leah Remini, whose tell-all, Troublemaker: Surviving Hollywood and Scientology, hits shelves next week.

Journalist Dan Harris, who interviewed Remini, teased the special on Good Morning America earlier today. Harris shared story from Remini about being written up by a church official for making a comment after seeing Tom "forcibly kissing Katie," in her words.

Admittedly, we don't know what, or how much, Holmes will say about her experience in the church — or what it was like being married to its poster boy. In fact, she may only speak on Remini specifically. But the fact that Holmes is finally breaking her silence on the issue is what's most significant here, because Scientology's infamous image-management tactic is largely about keeping ex-members silent.

We already got an unprecedented glimpse into the inner workings of the church from former members who spoke out in HBO's landmark documentary Going Clearearlier this year.

But nobody so close to Cruise — the couple were married for almost six years — has ever spoken out. In 2013, TMZ reported that Cruise's affiliation with the organization was an issue involved in his divorce from Holmes. Will she reveal anything about her ex specifically? Not likely. As Remini explains in a preview of the interview, "Being critical of Tom Cruise is being critical of Scientology itself... You are evil."

Watch the sneak peek below, and tune into ABC at 10 p.m. tonight for the full special. Who knows, this might even be worth canceling your Halloween eve plans for.